In ENVI's orthorectification process (starting with Build RCPs in this tutorial: http://www.rsinc.com/Envi...Orthorect_Aerial.pdf ), after building the interior and exterior orientation, I try to bring in my DEM and it says that the DEM and the image do not match (not sure if that is exactly what it said). What I have is a large rectangular DEM of the area and the aerial photograph I am trying to orthorectify lies within the DEM. Do I have to create a clip within the DEM of the aerial photograph location? Does anyone have an idea because I'm not sure where to start? Also, I have to process about 60+ images, anyone know of an automatic way to do this, or a faster way? Thanks in advance,